While the development of waterbeds has provided a new concept in sleeping comfort, there have been a series of problems associated with these devices. Perhaps the best known is the wave phenomenon. That is, a force suddenly applied to one portion of a waterbed mattress results in a propagation of a wave across the mattress which is then bounced off the wall of the mattress and returned somewhat in the manner of a wave in a swimming pool. Previous inventive efforts to minimize the wave phenomenon have largely involved the insertion of baffles into the mattress structure or floating material on top of the water surface that resists the wave phenomenon. These developments have had some moderate success in reducing the wave phenomenon, but usually do not completely eliminate that problem.
A second common problem has been the hammock-like support experienced by user of waterbeds. Hammock-like support is inherent in the construction of ordinary waterbed mattresses, because body support is accomplished mainly by a taut flexible material which contains the water and there results a disposition of the body such that the trunk is in a lowermost position with the legs and arms and head thrust upward and outward. Nothing illustrates this better than the uncomfortable tendency of two people who "roll together" when they lie close together on a waterbed. Since hammock-like support is not truly comfortable, it remains a point of dissatisfaction for many waterbed users. Insertion of materials within the mattress, such as those inserted to reduce waves, provide minimal improvement in this problem.
A third problem concerns the bottoming effect, which results because a conventional waterbed mattress is placed upon a rigid plane to provide uniform support for the entire lower surface of the waterbed mattress. The conventional solution to this problem has been to use nine to twelve inch deep waterbed mattresses in an attempt to create sufficient depth in the mattress to avoid reaching bottom when a sudden localized force is applied. Even so, it is still possible with this depth of water to hit bottom with a sudden localized force, and this attempted solution leads to several additional waterbed problems which tend to be inherent with the waterbed concept, but are aggravated by the deep fill attempted solution to the bottoming effect.
A great many waterbeds are made with a frame which contains the periphery of the waterbed mattress. Particularly when a deep fill solution is attempted to resolve the bottoming effect, a large lateral outward force is generated against the containing frame, so that massive (usually two 2".times.10") timbers are necessary to withstand it. These are uncomfortable to sit upon, and even if padded, create a strong tendency to tumble inward when sat upon. Thus, the deep fill solution to the bottoming effect increases the need for a lateral frame, which in turn causes the tumble inward difficulty and edge sitting discomfort difficulty as collateral problems.
Moreover, the deep fill solution makes the waterbed extremely heavy. With a nine inch or greater fill, the water alone weighs about two thousand pounds, and massive structure is required to support the mattress both vertically and laterally. Many residential structures were never designed to support such a large concentration of weight as results from such a piece of furniture, giving rise to very reasonable concerns on the part of both waterbed owners and their landlords.
In addition, the large volume of water becomes too great of a quantity to readily reach thermal equilibrium with typical cyclical variations in ambient room temperature on a daily basis. Accordingly, substantial condensation takes place on the waterbed surface unless the water within the mattress is heated to a temperature that prevents such condensation. Usually electric heaters are employed with automatic or semi-automatic controls, but there is the additional expense of acquisition and especially the cost of operation which may be up to $250.00 per year in northern climates. Some would also argue that such electrical heating apparatus represents a safety hazard in close proximity to such a large volume of water.
Consequently, the actually unsuccessful deep fill solution to bottoming effect creates, at least in part, a number of collateral concerns which include edge sitting discomfort, the tumble in effect, tremendous weight, lack of thermal equilibrium with cyclic room temperature variations, the necessity to heat the water and to control that heating, and finally, the consequent safety hazard. Furthermore, there still exists the problems of eliminating the wave phenomenon and the hammock-like support discomfort.